bus/at-spi-bus-launcher.c

   1 /* -*- mode: c; c-basic-offset: 2; indent-tabs-mode: nil; -*-
   2  *
   3  * at-spi-bus-launcher: Manage the a11y bus as a child process
   4  *
   5  * Copyright 2011 Red Hat, Inc.
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Library General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Library General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Library General Public
  18  * License along with this library; if not, write to the
  19  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20  * Boston, MA 02111-1307, USA.
  21  */
  22
  23 #include "config.h"
  24
  25 #include <unistd.h>
  26 #include <string.h>
  27 #include <signal.h>
  28 #include <sys/wait.h>
  29 #include <errno.h>
  30 #include <stdio.h>
  31
  32 #include <gio/gio.h>
  33 #include <X11/Xlib.h>
  34 #include <X11/Xatom.h>
  35
  36 typedef enum {
  37   A11Y_BUS_STATE_IDLE = 0,
  38   A11Y_BUS_STATE_READING_ADDRESS,
  39   A11Y_BUS_STATE_RUNNING,
  40   A11Y_BUS_STATE_ERROR
  41 } A11yBusState;
  42
  43 typedef struct {
  44   GMainLoop *loop;
  45   gboolean launch_immediately;
  46   gboolean a11y_enabled;
  47   GDBusConnection *session_bus;
  48   GSettings *desktop_schema;
  49
  50   A11yBusState state;
  51   /* -1 == error, 0 == pending, > 0 == running */
  52   int a11y_bus_pid;
  53   char *a11y_bus_address;
  54   int pipefd[2];
  55   char *a11y_launch_error_message;
  56 } A11yBusLauncher;
  57
  58 static A11yBusLauncher *_global_app = NULL;
  59
  60 static const gchar introspection_xml[] =
  61   "<node>"
  62   "  <interface name='org.a11y.Bus'>"
  63   "    <method name='GetAddress'>"
  64   "      <arg type='s' name='address' direction='out'/>"
  65   "    </method>"
  66   "  </interface>"
  67   "<interface name='org.a11y.Status'>"
  68   "<property name='IsEnabled' type='b' access='readwrite'/>"
  69   "</interface>"
  70   "</node>";
  71 static GDBusNodeInfo *introspection_data = NULL;
  72
  73 static void
  74 setup_bus_child (gpointer data)
  75 {
  76   A11yBusLauncher *app = data;
  77   (void) app;
  78
  79   close (app->pipefd[0]);
  80   dup2 (app->pipefd[1], 3);
  81   close (app->pipefd[1]);
  82
  83   /* On Linux, tell the bus process to exit if this process goes away */
  84 #ifdef __linux
  85 #include <sys/prctl.h>
  86   prctl (PR_SET_PDEATHSIG, 15);
  87 #endif
  88 }
  89
  90 /**
  91  * unix_read_all_fd_to_string:
  92  *
  93  * Read all data from a file descriptor to a C string buffer.
  94  */
  95 static gboolean
  96 unix_read_all_fd_to_string (int      fd,
  97                             char    *buf,
  98                             ssize_t  max_bytes)
  99 {
 100   ssize_t bytes_read;
 101
 102   while (max_bytes > 1 && (bytes_read = read (fd, buf, MAX (4096, max_bytes - 1))))
 103     {
 104       if (bytes_read < 0)
 105         return FALSE;
 106       buf += bytes_read;
 107       max_bytes -= bytes_read;
 108     }
 109   *buf = '\0';
 110   return TRUE;
 111 }
 112
 113 static void
 114 on_bus_exited (GPid     pid,
 115                gint     status,
 116                gpointer data)
 117 {
 118   A11yBusLauncher *app = data;
 119
 120   app->a11y_bus_pid = -1;
 121   app->state = A11Y_BUS_STATE_ERROR;
 122   if (app->a11y_launch_error_message == NULL)
 123     {
 124       if (WIFEXITED (status))
 125         app->a11y_launch_error_message = g_strdup_printf ("Bus exited with code %d", WEXITSTATUS (status));
 126       else if (WIFSIGNALED (status))
 127         app->a11y_launch_error_message = g_strdup_printf ("Bus killed by signal %d", WTERMSIG (status));
 128       else if (WIFSTOPPED (status))
 129         app->a11y_launch_error_message = g_strdup_printf ("Bus stopped by signal %d", WSTOPSIG (status));
 130     }
 131   g_main_loop_quit (app->loop);
 132 }
 133
 134 static gboolean
 135 ensure_a11y_bus (A11yBusLauncher *app)
 136 {
 137   GPid pid;
 138   char *argv[] = { DBUS_DAEMON, NULL, "--nofork", "--print-address", "3", NULL };
 139   char addr_buf[2048];
 140   GError *error = NULL;
 141
 142   if (app->a11y_bus_pid != 0)
 143     return FALSE;
 144
 145   argv[1] = g_strdup_printf ("--config-file=%s/at-spi2/accessibility.conf", SYSCONFDIR);
 146
 147   if (pipe (app->pipefd) < 0)
 148     g_error ("Failed to create pipe: %s", strerror (errno));
 149
 150   if (!g_spawn_async (NULL,
 151                       argv,
 152                       NULL,
 153                       G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD,
 154                       setup_bus_child,
 155                       app,
 156                       &pid,
 157                       &error))
 158     {
 159       app->a11y_bus_pid = -1;
 160       app->a11y_launch_error_message = g_strdup (error->message);
 161       g_clear_error (&error);
 162       goto error;
 163     }
 164
 165   close (app->pipefd[1]);
 166   app->pipefd[1] = -1;
 167
 168   g_child_watch_add (pid, on_bus_exited, app);
 169
 170   app->state = A11Y_BUS_STATE_READING_ADDRESS;
 171   app->a11y_bus_pid = pid;
 172   g_debug ("Launched a11y bus, child is %ld", (long) pid);
 173   if (!unix_read_all_fd_to_string (app->pipefd[0], addr_buf, sizeof (addr_buf)))
 174     {
 175       app->a11y_launch_error_message = g_strdup_printf ("Failed to read address: %s", strerror (errno));
 176       kill (app->a11y_bus_pid, SIGTERM);
 177       goto error;
 178     }
 179   close (app->pipefd[0]);
 180   app->pipefd[0] = -1;
 181   app->state = A11Y_BUS_STATE_RUNNING;
 182
 183   /* Trim the trailing newline */
 184   app->a11y_bus_address = g_strchomp (g_strdup (addr_buf));
 185   g_debug ("a11y bus address: %s", app->a11y_bus_address);
 186
 187   {
 188     Display *display = XOpenDisplay (NULL);
 189     if (display)
 190       {
 191         Atom bus_address_atom = XInternAtom (display, "AT_SPI_BUS", False);
 192         XChangeProperty (display,
 193                          XDefaultRootWindow (display),
 194                          bus_address_atom,
 195                          XA_STRING, 8, PropModeReplace,
 196                          (guchar *) app->a11y_bus_address, strlen (app->a11y_bus_address));
 197         XFlush (display);
 198         XCloseDisplay (display);
 199       }
 200   }
 201
 202   return TRUE;
 203
 204  error:
 205   close (app->pipefd[0]);
 206   close (app->pipefd[1]);
 207   app->state = A11Y_BUS_STATE_ERROR;
 208
 209   return FALSE;
 210 }
 211
 212 static void
 213 handle_method_call (GDBusConnection       *connection,
 214                     const gchar           *sender,
 215                     const gchar           *object_path,
 216                     const gchar           *interface_name,
 217                     const gchar           *method_name,
 218                     GVariant              *parameters,
 219                     GDBusMethodInvocation *invocation,
 220                     gpointer               user_data)
 221 {
 222   A11yBusLauncher *app = user_data;
 223
 224   if (g_strcmp0 (method_name, "GetAddress") == 0)
 225     {
 226       ensure_a11y_bus (app);
 227       if (app->a11y_bus_pid > 0)
 228         g_dbus_method_invocation_return_value (invocation,
 229                                                g_variant_new ("(s)", app->a11y_bus_address));
 230       else
 231         g_dbus_method_invocation_return_dbus_error (invocation,
 232                                                     "org.a11y.Bus.Error",
 233                                                     app->a11y_launch_error_message);
 234     }
 235 }
 236
 237 static GVariant *
 238 handle_get_property  (GDBusConnection       *connection,
 239                       const gchar           *sender,
 240                       const gchar           *object_path,
 241                       const gchar           *interface_name,
 242                       const gchar           *property_name,
 243                     GError **error,
 244                     gpointer               user_data)
 245 {
 246   A11yBusLauncher *app = user_data;
 247
 248   if (g_strcmp0 (property_name, "IsEnabled") == 0)
 249     {
 250       return g_variant_new ("b", app->a11y_enabled);
 251     }
 252   else
 253     return NULL;
 254 }
 255
 256 static void
 257 handle_a11y_enabled_change (A11yBusLauncher *app, gboolean enabled,
 258                                gboolean notify_gsettings)
 259 {
 260   GVariantBuilder *builder;
 261   GVariantBuilder *invalidated_builder;
 262
 263   if (enabled == app->a11y_enabled)
 264     return;
 265
 266   app->a11y_enabled = enabled;
 267
 268   if (notify_gsettings && app->desktop_schema)
 269     {
 270       g_settings_set_boolean (app->desktop_schema, "toolkit-accessibility",
 271                               enabled);
 272       g_settings_sync ();
 273     }
 274
 275   builder = g_variant_builder_new (G_VARIANT_TYPE_ARRAY);
 276   invalidated_builder = g_variant_builder_new (G_VARIANT_TYPE ("as"));
 277   g_variant_builder_add (builder, "{sv}", "IsEnabled",
 278                          g_variant_new_boolean (enabled));
 279
 280   g_dbus_connection_emit_signal (app->session_bus, NULL, "/org/a11y/bus",
 281                                  "org.freedesktop.DBus", "PropertiesChanged",
 282                                  g_variant_new ("(sa{sv}as)", "org.a11y.Status",
 283                                                 builder,
 284                                                 invalidated_builder),
 285                                  NULL);
 286 }
 287
 288 static gboolean
 289 handle_set_property  (GDBusConnection       *connection,
 290                       const gchar           *sender,
 291                       const gchar           *object_path,
 292                       const gchar           *interface_name,
 293                       const gchar           *property_name,
 294                       GVariant *value,
 295                     GError **error,
 296                     gpointer               user_data)
 297 {
 298   A11yBusLauncher *app = user_data;
 299
 300   if (g_strcmp0 (property_name, "IsEnabled") == 0)
 301     {
 302       const gchar *type = g_variant_get_type_string (value);
 303       gboolean enabled;
 304       if (g_strcmp0 (type, "b") != 0)
 305         {
 306           g_set_error (error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
 307                        "org.a11y.Status.IsEnabled expects a boolean but got %s", type);
 308           return FALSE;
 309         }
 310       enabled = g_variant_get_boolean (value);
 311       handle_a11y_enabled_change (app, enabled, TRUE);
 312       return TRUE;
 313     }
 314   else
 315     {
 316       g_set_error (error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
 317                        "Unknown property '%s'", property_name);
 318       return FALSE;
 319     }
 320 }
 321
 322 static const GDBusInterfaceVTable bus_vtable =
 323 {
 324   handle_method_call,
 325   NULL, /* handle_get_property, */
 326   NULL  /* handle_set_property */
 327 };
 328
 329 static const GDBusInterfaceVTable status_vtable =
 330 {
 331   NULL, /* handle_method_call */
 332   handle_get_property,
 333   handle_set_property
 334 };
 335
 336 static void
 337 on_bus_acquired (GDBusConnection *connection,
 338                  const gchar     *name,
 339                  gpointer         user_data)
 340 {
 341   A11yBusLauncher *app = user_data;
 342   GError *error;
 343   guint registration_id;
 344
 345   if (connection == NULL)
 346     {
 347       g_main_loop_quit (app->loop);
 348       return;
 349     }
 350   app->session_bus = connection;
 351
 352   if (app->launch_immediately)
 353     {
 354       ensure_a11y_bus (app);
 355       if (app->state == A11Y_BUS_STATE_ERROR)
 356         {
 357           g_main_loop_quit (app->loop);
 358           return;
 359         }
 360     }
 361
 362   error = NULL;
 363   registration_id = g_dbus_connection_register_object (connection,
 364                                                        "/org/a11y/bus",
 365                                                        introspection_data->interfaces[0],
 366                                                        &bus_vtable,
 367                                                        _global_app,
 368                                                        NULL,
 369                                                        &error);
 370   if (registration_id == 0)
 371     g_error ("%s", error->message);
 372
 373   g_dbus_connection_register_object (connection,
 374                                                        "/org/a11y/bus",
 375                                                        introspection_data->interfaces[1],
 376                                                        &status_vtable,
 377                                                        _global_app,
 378                                                        NULL,
 379                                                        &error);
 380 }
 381
 382 static void
 383 on_name_lost (GDBusConnection *connection,
 384               const gchar     *name,
 385               gpointer         user_data)
 386 {
 387   A11yBusLauncher *app = user_data;
 388   if (app->session_bus == NULL
 389       && connection == NULL
 390       && app->a11y_launch_error_message == NULL)
 391     app->a11y_launch_error_message = g_strdup ("Failed to connect to session bus");
 392   g_main_loop_quit (app->loop);
 393 }
 394
 395 static void
 396 on_name_acquired (GDBusConnection *connection,
 397                   const gchar     *name,
 398                   gpointer         user_data)
 399 {
 400   A11yBusLauncher *app = user_data;
 401   (void) app;
 402 }
 403
 404 static int sigterm_pipefd[2];
 405
 406 static void
 407 sigterm_handler (int signum)
 408 {
 409   write (sigterm_pipefd[1], "X", 1);
 410 }
 411
 412 static gboolean
 413 on_sigterm_pipe (GIOChannel  *channel,
 414                  GIOCondition condition,
 415                  gpointer     data)
 416 {
 417   A11yBusLauncher *app = data;
 418
 419   g_main_loop_quit (app->loop);
 420
 421   return FALSE;
 422 }
 423
 424 static void
 425 init_sigterm_handling (A11yBusLauncher *app)
 426 {
 427   GIOChannel *sigterm_channel;
 428
 429   if (pipe (sigterm_pipefd) < 0)
 430     g_error ("Failed to create pipe: %s", strerror (errno));
 431   signal (SIGTERM, sigterm_handler);
 432
 433   sigterm_channel = g_io_channel_unix_new (sigterm_pipefd[0]);
 434   g_io_add_watch (sigterm_channel,
 435                   G_IO_IN | G_IO_ERR | G_IO_HUP,
 436                   on_sigterm_pipe,
 437                   app);
 438 }
 439
 440 static gboolean
 441 already_running ()
 442 {
 443   Atom AT_SPI_BUS;
 444   Atom actual_type;
 445   Display *bridge_display;
 446   int actual_format;
 447   unsigned char *data = NULL;
 448   unsigned long nitems;
 449   unsigned long leftover;
 450   gboolean result = FALSE;
 451
 452   bridge_display = XOpenDisplay (NULL);
 453   if (!bridge_display)
 454               return FALSE;
 455
 456   AT_SPI_BUS = XInternAtom (bridge_display, "AT_SPI_BUS", False);
 457   XGetWindowProperty (bridge_display,
 458                       XDefaultRootWindow (bridge_display),
 459                       AT_SPI_BUS, 0L,
 460                       (long) BUFSIZ, False,
 461                       (Atom) 31, &actual_type, &actual_format,
 462                       &nitems, &leftover, &data);
 463
 464   if (data)
 465   {
 466     GDBusConnection *bus;
 467     GError *error = NULL;
 468     const gchar *old_session = g_getenv ("DBUS_SESSION_BUS_ADDRESS");
 469     /* TODO: Is there a better way to connect? This is really hacky */
 470     g_setenv ("DBUS_SESSION_BUS_ADDRESS", data, TRUE);
 471     bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
 472     g_setenv ("DBUS_SESSION_BUS_ADDRESS", old_session, TRUE);
 473     if (bus != NULL)
 474       {
 475         result = TRUE;
 476         g_object_unref (bus);
 477       }
 478   }
 479
 480   XCloseDisplay (bridge_display);
 481   return result;
 482 }
 483
 484 static GSettings *
 485 get_desktop_schema ()
 486 {
 487   const char * const *schemas = NULL;
 488   gint i;
 489
 490   schemas = g_settings_list_schemas ();
 491   for (i = 0; schemas[i]; i++)
 492   {
 493     if (!strcmp (schemas[i], "org.gnome.desktop.interface"))
 494       return g_settings_new (schemas[i]);
 495   }
 496
 497   return NULL;
 498 }
 499
 500 static void
 501 gsettings_key_changed (GSettings *gsettings, const gchar *key, void *user_data)
 502 {
 503   gboolean new_val = g_settings_get_boolean (gsettings, key);
 504   A11yBusLauncher *app = user_data;
 505
 506   if (strcmp (key, "toolkit-accessibility") != 0)
 507     return;
 508
 509   handle_a11y_enabled_change (_global_app, new_val, FALSE);
 510 }
 511
 512 int
 513 main (int    argc,
 514       char **argv)
 515 {
 516   GError *error = NULL;
 517   GMainLoop *loop;
 518   GDBusConnection *session_bus;
 519   int name_owner_id;
 520   gboolean a11y_set = FALSE;
 521   gint i;
 522
 523   g_type_init ();
 524
 525   if (already_running ())
 526     return 0;
 527
 528   _global_app = g_slice_new0 (A11yBusLauncher);
 529   _global_app->loop = g_main_loop_new (NULL, FALSE);
 530
 531   for (i = 1; i < argc; i++)
 532     {
 533       if (!strcmp (argv[i], "--launch-immediately"))
 534         _global_app->launch_immediately = TRUE;
 535       else if (sscanf (argv[i], "--a11y=%d", &_global_app->a11y_enabled) == 2)
 536         a11y_set = TRUE;
 537     else
 538       g_error ("usage: %s [--launch-immediately] [--a11y=0|1]", argv[0]);
 539     }
 540
 541   _global_app->desktop_schema = get_desktop_schema ();
 542
 543   if (!a11y_set)
 544     {
 545       _global_app->a11y_enabled = _global_app->desktop_schema
 546                                   ? g_settings_get_boolean (_global_app->desktop_schema, "toolkit-accessibility")
 547                                   : _global_app->launch_immediately;
 548     }
 549
 550   if (_global_app->desktop_schema)
 551     g_signal_connect (_global_app->desktop_schema,
 552                       "changed::toolkit-accessibility",
 553                       G_CALLBACK (gsettings_key_changed), _global_app);
 554
 555   init_sigterm_handling (_global_app);
 556
 557   introspection_data = g_dbus_node_info_new_for_xml (introspection_xml, NULL);
 558   g_assert (introspection_data != NULL);
 559
 560   name_owner_id = g_bus_own_name (G_BUS_TYPE_SESSION,
 561                                   "org.a11y.Bus",
 562                                   G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT,
 563                                   on_bus_acquired,
 564                                   on_name_acquired,
 565                                   on_name_lost,
 566                                   _global_app,
 567                                   NULL);
 568
 569   g_main_loop_run (_global_app->loop);
 570
 571   if (_global_app->a11y_bus_pid > 0)
 572     kill (_global_app->a11y_bus_pid, SIGTERM);
 573
 574   /* Clear the X property if our bus is gone; in the case where e.g.
 575    * GDM is launching a login on an X server it was using before,
 576    * we don't want early login processes to pick up the stale address.
 577    */
 578   {
 579     Display *display = XOpenDisplay (NULL);
 580     if (display)
 581       {
 582         Atom bus_address_atom = XInternAtom (display, "AT_SPI_BUS", False);
 583         XDeleteProperty (display,
 584                          XDefaultRootWindow (display),
 585                          bus_address_atom);
 586
 587         XFlush (display);
 588         XCloseDisplay (display);
 589       }
 590   }
 591
 592   if (_global_app->a11y_launch_error_message)
 593     {
 594       g_printerr ("Failed to launch bus: %s", _global_app->a11y_launch_error_message);
 595       return 1;
 596     }
 597   return 0;
 598 }